Answer:
C. 25 N
Step-by-step explanation:
w = Weight of box = 80 N
= Coefficient of kinetic friction = 0.25
= Coefficient of static friction = 0.5
F = Pulling force = 25 N
Static friction


The force of pulling is less than the static frictional force so this makes the friction force equal to the force of pulling.
So, the friction force on the box is 25 N.